Systems and methods for manufacturing electrodes using increased roll size gradients
By using a multi-roll calendering process with an increased roll size gradient to manufacture rechargeable lithium-ion battery electrodes with a thickness of less than 80μm, the problem of the difficulty in manufacturing thin electrodes by traditional dry processes has been solved, enabling battery applications with high energy density and low self-discharge rate.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-21
- Publication Date
- 2026-03-03
AI Technical Summary
Existing technologies struggle to efficiently manufacture rechargeable lithium-ion battery electrodes, especially cathode electrodes, with a thickness of less than 100 μm. There is room for improvement in traditional dry processes.
A multi-roll calendering process is adopted, which utilizes the increased roller size gradient to gradually reduce the thickness of the active material film through a series of roller groups, and finally laminates it onto the current collector to form an electrode sheet with a thickness of less than 80μm.
It has achieved efficient manufacturing of high-nickel cathode electrodes with a thickness of less than 80 μm, providing rechargeable lithium-ion batteries with high energy density and low self-discharge rate, suitable for electric vehicles and hybrid vehicles.
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Figure CN121601550A_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to a method for manufacturing a battery cell, and more specifically, to a method for manufacturing electrodes for a battery cell using an increasing roller size gradient. Background Technology
[0002] Compared to older types of rechargeable batteries (such as nickel-metal hydride, nickel-cadmium, or lead-acid batteries), rechargeable lithium-ion batteries maintain relatively high energy density, relatively low internal resistance, and low self-discharge rate when not in use. Electric vehicles and hybrid vehicles primarily use rechargeable lithium-ion batteries as a reliable power source because lithium-ion batteries are capable of repeated power cycles throughout their lifespan.
[0003] A rechargeable lithium-ion battery cell typically includes a positive electrode, a negative electrode, an electrolyte, and a separator layer disposed between the positive and negative electrodes. The positive electrode is called the cathode electrode and includes a layer of cathode active material disposed on a cathode current collector. The negative electrode is called the anode electrode and includes a layer of anode active material disposed on an anode current collector.
[0004] Electrodes can be manufactured using solvent-free electrode fabrication processes (also known as dry processes), which are advantageous compared to processes that require solvents. Besides eliminating solvents, dry processes eliminate the need for drying equipment and time, thus reducing footprint and manufacturing costs. In a dry process, one or more pairs of calendering rolls compress a dry mixture of active material, binder, and other materials to form an active electrode layer of the desired thickness, which is then laminated onto a current collector. Dry processes are suitable for preparing active material layers thicker than 100 micrometers (μm). However, some electrodes require lower active material layer thicknesses for improved performance and / or encapsulation considerations.
[0005] Therefore, while traditional solvent-free electrode fabrication methods have achieved their intended purpose, more efficient methods are needed to manufacture electrodes with active material layer thicknesses of less than 100 μm. Summary of the Invention
[0006] According to several aspects, a system for manufacturing electrode sheets is provided. The system includes multiple sets of rollers configured to calender an active material film having an initial thickness. As the active material film is calendered through the multiple sets of rollers, the initial thickness continuously decreases. The multiple sets of rollers include a first set of rollers and a second set of rollers disposed immediately downstream of the first set of rollers. The first set of rollers includes a first roller radius, and the second set of rollers includes a second roller radius larger than the first roller radius.
[0007] In another aspect of this disclosure, the multiple sets of rollers also include an Nth set of rollers, where N is an integer greater than 2. The Nth set of rollers includes a Nth roller radius that is larger than the roller radius of any set of rollers preceding the Nth set.
[0008] In another aspect of this disclosure, the first set of rollers is a first pair of rollers, comprising a first pair of first rollers and a first pair of second rollers spaced apart from the first pair of first rollers, with a first pair of gaps (G1) defined between the first pair of first rollers and the first pair of second rollers. The second set of rollers is a second pair of rollers, comprising a second pair of first rollers and a second pair of second rollers spaced apart from the second pair of first rollers, with a second pair of gaps (G2) defined between the second pair of first rollers and the second pair of second rollers, wherein G2 is equal to or less than G1.
[0009] In another aspect of this disclosure, the first set of rollers includes a first pair of rollers having a first pair of first rollers and a first pair of second rollers. The second set of rollers includes a second pair of rollers having a second pair of first rollers and a second pair of second rollers. Each of the first pair of first rollers and the first pair of second rollers includes a first set of roller radius (R1). Each of the second pair of first rollers and the second pair of second rollers includes a second set of roller radius (R2), wherein R2 is greater than R1.
[0010] In another aspect of this disclosure, the multiple sets of rollers also include an Nth set of rollers, where N is an integer greater than 2. The Nth set of rollers includes an Nth roller radius (RN) greater than R2.
[0011] In another aspect of this disclosure, the first set of rollers includes at least two rollers of a first group having a first group roller radius R1. The second set of rollers includes at least two rollers of a second group having a second group roller radius R2, wherein R2 is greater than R1.
[0012] In another aspect of this disclosure, the first set of rollers includes a first set of end rollers. The second set of rollers includes a second set of front rollers. The second set of front rollers is disposed adjacent to the first set of end rollers, and a set gap (GA) is defined between the second set of front rollers and the first set of end rollers.
[0013] In another aspect of this disclosure, the first pair of first rollers may rotate at a different speed relative to the first pair of second rollers.
[0014] In another aspect of this disclosure, at least one of the multiple sets of rollers can be heated to a temperature of 80°C to 200°C.
[0015] In another aspect of this disclosure, the active material membrane includes an adhesive comprising polytetrafluoroethylene (PTFE).
[0016] According to several aspects, a method for manufacturing a cathode sheet is provided. The method includes calendering an active material film using a series of rolls. Each subsequent roll has a larger diameter than the rolls of the preceding rolls to reduce the thickness of the active material film to less than 80 micrometers. The original active material film comprises more than 80 weight percent nickel (Ni) and a binder comprising polytetrafluoroethylene (PTFE). The active material film comprises LiNi in a weight ratio of 95:3:2. 0.8Co 0.1 Mn 0.1 O2(NCM811): Super P carbon (SP): PTFE.
[0017] In another aspect of this disclosure, multiple sets of rollers are multiple pairs of rollers having the same radius. One roller in a pair rotates at a different speed relative to the other roller in that pair.
[0018] In another aspect of this disclosure, the multiple sets of rollers include a first set of rollers and a second set of rollers disposed immediately downstream of the first set of rollers. The first set of rollers includes a first roller radius, and the second set of rollers includes a second roller radius larger than the first roller radius.
[0019] According to several aspects, a method for manufacturing a cathode sheet is provided. The method includes calendering an active material film having an initial thickness using multiple sets of rolls to reduce the initial thickness to a predetermined production thickness, and laminating the calendered active material film onto a current collector. The multiple sets of rolls are arranged in a calendering sequence with the roll radius increasing from smallest to largest.
[0020] Further applicability will become apparent from the description provided herein. It should be understood that the specification and specific examples are for illustrative purposes only and are not intended to limit the scope of this disclosure. Attached Figure Description
[0021] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of this disclosure in any way.
[0022] Figure 1 This is a cross-sectional view of a rechargeable battery according to an exemplary embodiment;
[0023] Figure 2 This is a schematic diagram of a system for manufacturing electrodes using an increased roller size gradient according to an exemplary embodiment;
[0024] Figure 3 This is a schematic diagram of a system for manufacturing electrodes using an increased roller size gradient according to another exemplary embodiment; and
[0025] Figure 4 This is a block diagram of a method for manufacturing electrodes using an increased roller size gradient according to an exemplary embodiment. Detailed Implementation
[0026] The following description is merely exemplary in nature and is not intended to limit this disclosure, its application, or its uses. The illustrated embodiments are disclosed with reference to the accompanying drawings, in which the same reference numerals denote corresponding parts in multiple drawings. The drawings are not necessarily drawn to scale, and some features may be enlarged or minimized to show detail of particular features. The specific structural and functional details disclosed are not intended to be construed as limiting, but rather as a representative basis for teaching those skilled in the art how to practice the disclosed concepts.
[0027] When an element or layer is referred to as “in,” “joined to,” “connected to,” “attached to,” or “coupled to” another element or layer, it may be directly in, joined to, connected to, attached to, or coupled to the other element or layer, or there may be intermediate elements or layers present. Conversely, when an element is referred to as “directly in,” “directly joined to,” “directly connected to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intermediate elements or layers present. Other terms used to describe relationships between elements should be interpreted in a similar manner (e.g., “between” vs. “directly between,” “adjacent” vs. “directly adjacent,” etc.). As used herein, the term “and / or” includes any and all combinations of one or more of the related listed items.
[0028] The terms “first,” “third,” etc., may be used herein to describe various elements, components, regions, layers, and / or parts. These elements, components, regions, layers, and / or parts should not be limited by these terms. These terms may be used only to distinguish one element, component, region, layer, or part from another. Terms such as “first,” “second,” and other numerical terms do not imply order or sequence unless the context clearly indicates otherwise. Therefore, without departing from the teachings of the example configuration, the first element, component, region, layer, or part discussed below may be referred to as the second element, component, region, layer, or part.
[0029] Figure 1 This is an illustration of a rechargeable battery (such as a rechargeable lithium-ion battery), typically denoted by reference numeral 100 and also referred to as battery 100. Battery 100 includes a negative electrode 102, a positive electrode 104, and a separator layer 108 disposed between the negative electrode 102 and the positive electrode 104. Separator layer 108 includes an electrolyte material suitable for conducting lithium ions between the negative electrode 102 and the positive electrode 104. The negative electrode 102 includes a lithium-accepting active material 103, and the positive electrode 104 includes a lithium-based active material 105, which can store lithium ions at a higher potential than the lithium-accepting host material 103 of the negative electrode 102. A binder comprising polytetrafluoroethylene (PTFE) is bonded to the lithium-accepting active material 103 and the lithium-based active material 105.
[0030] The positive electrode 104 is also referred to as the cathode 104 due to its higher electrochemical potential, while the negative electrode 102 is also referred to as the anode 102 due to its relatively lower electrochemical potential. Each of the lithium-accepting active material 103 of the anode and the lithium-based active material 105 of the cathode is laminated onto the corresponding current collectors 112 and 114. The current collectors 112 and 114 may be formed of conductive metals, such as copper for the negative electrode 102 and aluminum for the positive electrode 104.
[0031] Figure 2 and Figure 3 These are schematic diagrams of alternative embodiments of systems 200 and 300 that manufacture electrodes using a continuous set of rollers with an increasing roller size gradient. The alternative embodiments of systems 200 and 300 are configured to calender a raw active material film 201 through a series of rollers and laminate the calendered active material film (also referred to as a calendered active material layer) onto a current collector to form an electrode sheet. The system is operated to output electrode sheets 213 at a predetermined production line speed (also referred to as linear speed) in steady state, which can be measured in production units per minute. The linear speed used to produce the electrode sheets can be expressed as the linear length of the electrode sheets produced per unit time, for example, feet per minute (ft / min).
[0032] Non-limiting examples of the composition of the original active material film include an active material, a binder composed of polytetrafluoroethylene (PTFE), and optionally one or more conductive additives, such as conductive carbon and / or conductive polymers. The active material depends on whether the final manufactured electrode sheet is a cathode or anode. In a non-limiting example of manufacturing a cathode electrode sheet, the active material includes a cathode active material, such as LiNi in a weight ratio of 95:3:2. 0.8 Co 0.1 Mn 0.1 O2(NCM811):Super P carbon (SP):PTFE. In a non-limiting example of manufacturing the anode electrode sheet, the active material includes an anode active material, such as graphite (Gr):SP:PTFE in a weight ratio of 97:1:2.
[0033] The primary active material membrane 201 can be manufactured by first preparing a dry mixture of active material, PTFE binder, and optional conductive additives. This dry mixture is also known as an electrode powder mixture. The electrode powder mixture undergoes shear fibrillation and a pre-calendering process to form the primary active material membrane 201. The pre-calendering process may include compressing the electrode powder mixture material through multiple pairs of heated rollers to form a monolithic, continuous primary active material membrane 201. The primary active material membrane 201 can be rolled into a roll 203 for use such as... Figure 2 and Figure 3 In systems 200 and 300 shown.
[0034] refer to Figure 2The system 200 includes a film roll distributor 203, a continuous pair of rollers 202 having increasing roller diameters (radii), and a lamination unit 209. The film roll distributor 203 is configured to hold the roll of the original active material film 201 and feed the original active material film 201 to the continuous pair of rollers 202 for calendering, thereby reducing the thickness of the original active material film 201 as it advances through the continuous pair of rollers 202.
[0035] In the illustrated embodiment, system 200 includes multiple pairs of rollers 202A-202N arranged in series during calendering to reduce the thickness of the original active material film 201. Generally, during the calendering process, subsequent pairs of rollers have larger diameters than the preceding pairs, denoted as radii R1, R2, RN. However, adjacent pairs of rollers can have the same roller diameter to improve the quality of the calendered active material film. For a specific pair of rollers, the roller radii are the same; however, the roller rotation speeds can be different.
[0036] System 200 includes at least a first pair of rollers 202A, a second pair of rollers 202B, and at most an Nth pair of rollers 202N, where N is an integer greater than 2. The original active material film 201 is fed to the first pair of rollers 202A, then to the second pair of rollers 202B, and, if equipped, through the Nth pair of rollers 202N. After calendering, the calendered active material layer 207 is fed to a laminating unit 209 to laminate the calendered active material layer 207 with a current collector 211, thereby forming an electrode sheet 213. The electrode sheet 213 is shown as being collected on a roll.
[0037] The first pair of rollers 202A includes a first pair of first rollers 202A1 and a first pair of second rollers 202A2. The first pair of first rollers 202A1 and the first pair of second rollers 202A2 are spaced apart to define a first pair of roller gaps (G1) therebetween. Each of the first pair of first rollers 202A1 and the first pair of second rollers 202A2 includes a radius R1. The second pair of rollers 202B includes a second pair of first rollers 202B1 and a second pair of second rollers 202B2. The second pair of first rollers 202B1 and the second pair of second rollers 202B2 are spaced apart to define a second pair of gaps (G2) therebetween. Each of the second pair of first rollers 202B1 and the second pair of second rollers 202B2 includes a radius R2. The Nth pair of rollers 202N includes an Nth pair of first rollers 202N1 and an Nth pair of second rollers 202N2. The Nth pair of first rollers 202N1 and the Nth pair of second rollers 202N2 are spaced apart to define a Nth pair of gaps (GN) therebetween. Each of the Nth pair of first rollers 202N1 and the Nth pair of second rollers 202N2 includes a radius RN.
[0038] The radius of the Nth pair of rolls (RN) is greater than the radius of the second pair of rolls (R2), and the radius of the second pair of rolls (R2) is greater than the radius of the first pair of rolls (R1) (RN>R2>R1). The gap (GN) of the Nth pair is equal to or less than the gap (G2) of the second pair, and the gap (G2) of the second pair is equal to or less than the gap (G1) of the first pair (GN≤G2≤G1). The smaller initial diameter of the multiple pairs of rolls 202A facilitates the formation of PTFE fibrils and gradually reduces the thickness of the active material film, while avoiding early over-densification. Subsequent pairs of rolls along the calendering process have a larger diameter (i.e., radius) than the preceding pairs. Sometimes, adjacent pairs of rolls can have the same roll diameter before transitioning to the next pair with a larger diameter to produce a high-quality calendered active material layer 207.
[0039] Each pair of rollers can be driven individually by a single motor and / or each pair of rollers can be driven by a single motor. The speed, or revolutions per minute (RPM), of each pair of rollers is controlled to output the desired production line rate. Because the circumference of the second pair of rollers 202B is greater than that of the first pair of rollers 202A, the second pair of rollers 202B can rotate at a lower RPM to achieve a predetermined linear speed compared to the first pair of rollers 202A. For each pair of rollers, the first and second rollers forming a pair can have a speed ratio differing from each other by 1.0 to 2.0. All rollers can be heated to an upper limit temperature of 80°C to 200°C.
[0040] Figure 3 This is a schematic diagram of another embodiment of a system (system 300) for manufacturing electrodes using multiple sets of progressively larger gradient rollers. System 300 includes a film roll distributor 203, multiple sets of rollers 302 connected in series, and a lamination unit 209. Each set of rollers 302A, 302B, 302C, 302N includes two or more rollers with the same diameter (i.e., 302A1, 302A2 for a set of rollers 302A). During calendering, each subsequent set of rollers includes a roller with a larger diameter than the immediately preceding set. The original active material film 201 is fed to the first set of rollers 302A, through the second set of rollers 302B, the third set of rollers 302C, and, if equipped, through the Nth set of rollers 302N. The last roller in a set of rollers calenders the original active material film in conjunction with the first roller in the immediately following set (i.e., rollers 302A1 and 302B1 cooperate), and transitions the active material film 201 from one set of rollers to the next. After calendering, the calendered active material layer 207 is fed to the laminating unit 209 to laminate the calendered active material layer 207 with the current collector 211, thereby forming the electrode sheet 213. Then, the electrode sheet 213 is collected onto a roll.
[0041] The multiple sets of rollers 302 include at least a first set of rollers 302A, a second set of rollers 302B, and optionally at most an Nth set of rollers 302N, where N is an integer greater than 2. The first set of rollers 302A includes multiple first-group rollers 302A1 and 302A2 having the same first roller radius (R1). The second set of rollers 302B includes multiple second-group rollers 302B1 and 302B2 having the same second roller radius (R2). The Nth set of rollers 302N includes multiple Nth-group rollers 302N1 and 302N2 having the same Nth roller radius (RN). The Nth roller radius (RN) is greater than the second roller radius (R2), and the second roller radius (R2) is greater than the first roller radius (R1) (RN>R2>R1).
[0042] In the illustrated embodiment, the first set of rollers 302 includes a first set of first rollers 302A1 and a first set of last rollers 302A2. In one embodiment, there may be multiple sets of first rollers between the first set of first rollers 302A1 and the first set of last rollers 302A2. The second set of rollers 302B includes a second set of first rollers 302B1 and a second set of last rollers 302B2. The first set of last rollers 302A2 is adjacent to and cooperates with the second set of first rollers 302B1 to calender the raw material film 201 as it transitions from the first set of rollers 302A1 to the larger diameter second set of rollers 302B1. The process continues, wherein the last roller in one set cooperates with the larger diameter first roller in the next set to calender the raw material film. Sometimes, multiple adjacent sets of rollers may have the same roller diameter before transitioning to the next set of rollers with a larger diameter to produce a high-calendered active material layer 207.
[0043] The first group of first rollers 302A1 and the first group of second rollers 302A2 are spaced apart to define a first group roller gap (G1) therebetween. The second group of first rollers 302B1 is disposed adjacent to the first group of second rollers 302A2, defining a gap A (GA) therebetween. The second group of first rollers 302B1 and the second group of second rollers 302B2 are spaced apart to define a second group gap (G2) therebetween. The second group roller gap (G2) is equal to or less than the first group roller gap (G1) (G2 => G1).
[0044] In systems 200 and 300, as the active material film is fed between two adjacent rollers, it is primarily subjected to shear forces in the feed zone and compressive forces in the roll gap zone. The larger-radius roller applies a higher clamping force to the active material film, resulting in a denser, compressed active material layer. However, this higher clamping force makes it difficult for the film to flow and shear through the gap between the two rollers to form electrodes. By using a smaller-radius roller in the initial stage of the calendering process, a lower clamping force can be achieved, providing a "light" pressure that is beneficial for reducing film thickness. A balance between shear and clamping requirements is achieved by providing rollers with a gradient increase in roller radius as the film advances during calendering.
[0045] Figure 4 This is a block diagram of a method 400 for manufacturing an electrode using an increased gradient roller size according to an exemplary embodiment. In block 402, a dry powder mixture of an active material, a PTFE binder, and optional conductive additives is prepared. The active material may be an active material for an anode active material or an active material for a cathode active material. In the case of a cathode active material, the cathode active material comprises lithium nickel cobalt aluminum oxide (NCMA) having a nickel content greater than 80 wt%.
[0046] In box 404, the dry powder mixture is subjected to high shear force fibrillation. Non-limiting examples include processing the dry powder mixture using a twin-screw extruder and / or jet mill to form a homogeneous mixture of electrode powder mixture materials.
[0047] In frame 406, the electrode powder mixture material is pre-calendered by multiple pairs of heated rollers to form a monolithic continuous original active material film with a thickness of 80 μm or less.
[0048] In frame 408, the original active material film is calendered by a series of rolls, wherein each subsequent roll has a larger diameter than the preceding rolls to reduce the thickness of the original active material film. In some embodiments, two or more adjacent rolls with the same radius may be present.
[0049] In frame 410, a calendered active material layer (electrode layer) with reduced thickness is laminated onto the current collector to form an electrode sheet.
[0050] The method 400 described above, performed in systems 200 and 300, enables the fabrication of high-nickel cathodes with a thickness of less than 80 μm, typically having a nickel content of over 80%. Examples of such high-nickel cathodes include lithium nickel cobalt aluminum oxide (NCMA) cathodes with a thickness of 75 μm or less, providing 5.0 mAh / cm². 2 The capacity load.
[0051] Numerical data are presented herein in a range format. The term "about" as used herein is known to those skilled in the art. Alternatively, the term "about" may include a specified value plus or minus 0.5%. It should be understood that this range format is used merely for convenience and brevity and should be flexibly interpreted to include not only the numerical values explicitly listed as range limits, but also all individual numerical values or subranges covered within that range, as if each numerical value and subrange were explicitly described. While examples have been described in detail, those skilled in the art to which this disclosure pertains will recognize various alternative designs and examples for practicing the disclosed methods within the scope of the appended claims.
[0052] The description in this disclosure is merely exemplary in nature, and any changes that do not depart from the spirit and scope of this disclosure are intended to fall within its scope. Such changes should not be considered as departing from the spirit and scope of this disclosure.
Claims
1. A system for manufacturing electrode sheets, comprising: Multiple sets of rollers are configured to calender an active material film having an initial thickness, wherein the initial thickness decreases as the active material film is calendered through the multiple sets of rollers. The multiple sets of rollers include a first set of rollers and a second set of rollers disposed immediately downstream of the first set of rollers; and Wherein, the first set of rollers includes a first roller radius, and the second set of rollers includes a second roller radius that is larger than the first roller radius.
2. The system according to claim 1, wherein, The multiple sets of rollers further include an Nth set of rollers, where N is an integer greater than 2; and Wherein, the Nth group of rollers includes a Nth roller radius that is larger than the roller radius of any group of rollers preceding the Nth group of rollers.
3. The system according to claim 1, wherein: The first set of rollers is a first pair of rollers, the first pair of rollers including a first pair of first rollers and a first pair of second rollers spaced apart from the first pair of first rollers, a first pair of gaps G1 defined between the first pair of first rollers and the first pair of second rollers; and The second set of rollers is a second pair of rollers, which includes a second pair of first rollers and a second pair of second rollers spaced apart from the second pair of first rollers. A second pair of gaps G2 is defined between the second pair of first rollers and the second pair of second rollers, wherein G2 is equal to or less than G1.
4. The system according to claim 1, wherein: The first set of rollers includes a first pair of rollers, the first pair of rollers having a first pair of first rollers and a first pair of second rollers; The second set of rollers includes a second pair of rollers, the second pair of rollers having a second pair of first rollers and a second pair of second rollers; Each of the first pair of first rollers and the first pair of second rollers includes a first set of roller radii R1; and Each of the second pair of first rollers and the second pair of second rollers includes a second set of roller radii R2, wherein R2 is greater than R1.
5. The system according to claim 4, wherein, The multiple sets of rollers also include an Nth set of rollers, where N is an integer greater than 2; and The Nth group of rollers includes the Nth roller radius RN, which is greater than R2.
6. The system according to claim 1, wherein: The first set of rollers includes at least two rollers of a first set having a first set roller radius R1; and The second set of rollers includes at least two rollers of the second set with a second set roller radius R2, wherein R2 is greater than R1.
7. The system according to claim 6, wherein: The first set of rollers includes a first set of end rollers; and The second set of rollers includes the second set of front rollers; as well as The second set of front rollers is arranged adjacent to the first set of end rollers, and a group gap GA is defined between the second set of front rollers and the first set of end rollers for calendering the active material film.
8. The system according to claim 3, wherein: The first pair of first rollers can rotate at different speeds relative to the first pair of second rollers.
9. The system according to claim 1, wherein, At least one of the multiple sets of rollers can be heated to a temperature of 80°C to 200°C.
10. The system according to claim 1, wherein, The active material membrane includes an adhesive, which includes polytetrafluoroethylene (PTFE).